Arms behind the back often indicates something to hide, but the exposed torso indicates someone who is trusting of those they are around.
If there were sound I wouldn't be surprised if he was caught for the moment in a pause, even a barely there pause, where his thought process is looking for the next word, so he repeats the previous word while his mind searches for the one he wants - but from the look on his face, he won't find the word, so he'll repeat his usual phrases until he can stumble on a new train of thought. Not brand new, but BRAND new - the new train of thought, for Trump, just means a jump to one of the short-ads he uses to advertise his brand.
Trump pretty much free associates from a defined set of terms and phrases. Those words and phrases are little more than jingles and cut-rate slogans really.
But I could be wrong. lol
Just having fun with the question. 
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